This application describes a developmental study of emotion, motivation, and decision-making in adolescence. The study focuses on the neural basis for affective changes during pubertal maturation, with an emphasis on sensation-seeking, reward-seeking, and risk-taking relevant to understanding adolescent vulnerability to substance use disorders. The design is aimed at disentangling puberty-dependent versus puberty-independent aspects of adolescent behavioral and brain development. This will be accomplished by comparing samples matched on age but differing in pubertal maturation and then re-studying each sample after two years of additional development. Measures at each time point will include: structural and functional imaging of neural systems mediating affective behaviors; behavioral measures of decision-making and inhibitory control; and experience-sampling measures of adolescents' mood, motivation, and reward-seeking behavior in their natural home environments. In addition, the study will examine the influence of heritable variation in monoamine function (dopamine and serotonin) on the development of these neural systems and affective behaviors. Through the convergence of these methodologies, this study aims at understanding maturational shifts in the functional relationships between limbic and prefrontal brain regions that may contribute to a transient increase in the tendency toward risky behavior and cause these behaviors to be experienced as more rewarding in adolescence--particularly in some individuals and in some social contexts. The short-term goals of this work are to test hypotheses about puberty-specific changes in affective brain systems that influence decision-making in adolescents and key sources of individual differences during this developmental period. The long-term goals of this work are to identify developmental pathways and biological mechanisms of vulnerability toward substance use disorders in ways that will inform early intervention and prevention strategies.